First, give it the -dxlevel 71 command line switch
Second, install the modded gma drivers from intel9xx.moonfruit.com
Third, use GMABooster and set it to 400 MHz (this does cause a SLIGHT increase in the drain on the battery, like going from 5 hours to 4 hrs 20 mins.
Finally, set everything to *low*. Low resolution, low model detail, etc
Hope this has been helpful!